Control of gaseous or liquid fluid flow and location within the operating specifications of valve seals requires use of certain materials that will not corrode or whose performance will not otherwise deteriorate due to the temperature or chemical composition of the fluid. For example, seals or O-rings have only certain temperature ranges, depending on the material of their composition, in which they are capable of performing their function of preventing leakage, cross-contamination, and failure due to inability to control fluid flow and location. Similarly, some seals or O-rings are not chemically compatible with certain kinds of fluids.
To control and contain fluid flow as desired when two or more different or distinct fluids are available to a valve, positive flow control is obtained by a complete shut-off by the valve piston as between the two different or distinct fluids. Depending on the means of force being applied to the valve piston, control of the fluid flow may also allow a specified portion of the fluid available to the valve to pass through it. If two or more different fluids are available to the valve, control and containment of the fluid flow may allow specified and controlled percentages of the full flow of each separate fluid to pass through the valve concurrently.
The three most common types of valve that are used to select as between or among two or more different or distinct liquid fluids available to the valve are: spool, ball and poppet valves.
A spool valve, which is used in hydraulic applications, may not be capable of forming a positive stop as between two or more different or distinct fluids available to the valve because it relies on mechanical tolerance between two different surfaces to attempt to do the sealing, rather than using an actual seal or O-ring. Therefore, a spool valve allows leakage and does not form a complete shut-off by the valve piston, as evidenced by the fact that commercial spool valves come with a leakage specification. The higher the temperature, the less viscous liquid fluids are likely to become, thereby making a complete shut-off by the spool valve piston even more problematic. Spool valves rely on high pressure to move liquid fluids. They do not have a free flow design for the liquid fluids that pass through them.
An opened ball valve does not have any restriction on the fluid that passes through it; it allows full flow of fluid passing through it. A non-motorized, three port, two position, ball valve cannot normally be driven by a solenoid because the stroke of a solenoid is not sufficiently long to cause the ball valve to engage in its complete sweep for selection between ports. Without a solenoid or motor, a non-motorized ball valve will not return to a default position when electrical power is removed, whereas a solenoid-driven valve will return to a default position. A motorized ball valve requires electrical power at all times to move; if electrical power is cut, then the motorized ball valve will not revert to a pre-determined default position. If electrical power is cut to a motorized ball valve, it will remain in its last position and two or more fluids available to the valve will continue to communicate with each other in the cavity or fluid passageway of the valve, as they were before electrical power was cut. If electrical power is cut unintentionally, the foregoing condition may leave the motorized ball valve in an undesired position and have other, unintended consequences.
A poppet valve is not a full flow valve, but it allows for a higher flow rate within its cavity or fluid passageway than does a spool valve of comparable diameter or aperture. Like a non-motorized ball valve, a poppet valve forms a positive stop as between and among two or more different and distinct fluids available to the valve. Unlike a ball valve, a poppet valve can be driven by a solenoid because its piston requires relatively small movement and only a short stroke. A poppet valve made in part of plastic material will not withstand higher temperatures and may deteriorate and fail if the fluid passing through it attains such temperatures. Commercially available poppet valves generally contain some plastic components.
If the portion of the valve control or selector rod, also known as the plunger, passing through the valve's cavity or fluid passageway, to which one or more valve pistons are attached or of which the valve pistons form a part, is made of a material such as mild steel, copper or brass, it may oxidize and corrode in the presence of certain liquid fluids, thus diminishing performance, contaminating the fluid liquid passing through it, and perhaps leading to a failure of functionality. If the portion of the valve control or selector rod that passes through the valve cavity or fluid passageway is made preferably of stainless steel, the chance for oxidation and corrosion will be minimized. If the liquid fluid consists of triglycerides, fatty acids, biodiesel (whether it meets ASTM Standard Specification 6751 or not), non-ester renewable diesel, hydro-processed esters and fatty acids, biojet fuel, or other biofuel, the portion of the valve control or selector rod that passes through the valve cavity or fluid passageway may also alternately and preferably be made of aluminum to minimize oxidation, contamination of the liquid fluid, and corrosion, though this portion of the valve control or selector rod can preferably and alternatively be made of more costly stainless steel. Triglycerides include the following substances: plant oil, pure plant oil, plant hydrocarbon oil, vegetable oil, fruit oil, animal fat, tallow, straight vegetable oil, waste vegetable oil, recycled vegetable oil, cooking oil, used cooking oil, yellow grease, and brown grease.
If the valve has hose clamp fittings, rather than JIC (Joint International Council) or NPT (National Pipe Thread) connectors, then it cannot be adapted to and used with more robust, industrial hosing and fittings. Commercially available valves typically have seals comprised of either silicon, nitrate or rubber. Silicon, nitrate and rubber seals are commonly used in valves but are not compatible with certain liquid fluids. For instance, rubber seals, when exposed to too low a level of aromatics in petroleum fuel or other fuel, will dry out, shrink and lose their sealing capability. Seals made of a fluoropolymer elastomer such as VITON® are more durable at higher temperatures than nitrate and rubber seals, are more resistant to some chemicals and solvents, and are fully compatible with biofuels, including triglycerides, fatty acids, and biodiesel. Biofuels run through a two-position, three-port valve, as one of two distinct fuels available to the valve, may need to be heated to reduce their viscosity prior to fuel injection. The valve body, if made of a material such as metal that efficiently conducts heat or cold, may perform the function of thermal transfer to the biofuel.
With regards to a solenoid operated valve, the portion of the valve control or selector rod, also known as the plunger, that goes into the solenoid should not be made of aluminum because it is not magnetic and will not respond to an electro-magnetic field and force created by the solenoid. Most stainless steel also is not magnetic and if it is not magnetic, then the portion of the plunger that goes into the solenoid, for the same reason, should not be made of it. The portion of the plunger that goes into the solenoid is preferably made of mild steel so that it will maximize the magnetic property of the solenoid and movement of its coil. If the valve is manual or gear driven or is driven by any other force or device that does not require a magnetic field, such as a vacuum, hydraulic, pneumatic or mechanical force, then the portion of the rod that goes into the solenoid need not preferably be made of mild steel, and it can optionally be made of the same material that the other components of the valve are made of, or of other materials. If the valve control or selector rod, also known as the plunger, is made of two or more sections composed of different materials, for example, one section is mild steel and an adjoining section is aluminum, then the two or more sections must be dielectrically isolated.
Needle valves, butterfly valves, gate valves, and other kinds of valves may be suitable for use as selector valves as between and among two or more different or distinct liquid fluids available to the valve, but due to their complexity and operational mechanics involved, often are not used for this purpose.
Some selector valves are pressure differential dependent. Typically, a pressure differential dependent valve is used when the fluid is gaseous, rather than liquid. A typical pressure differential dependent valve requires pressure on one side at all times to ensure a complete shut-off. If the pressure differential dependent valve does not always have pressure on this one side, then it may allow leakage or cross-contamination to occur as between or among two or more different or distinct liquid fluids available to the valve. If a valve is not pressure differential dependent, any other force besides pressure may be used to counterbalance the force or device driving the valve control or selector rod, also known as a plunger, and to keep the valve piston in its intended position. A spring is preferably used to counterbalance the driving force or device and return the plunger to its neutral or default position. If a solenoid is used as the driving force or device and the solenoid is capable of reversing magnetic poles, it can use the magnetic field to position the valve plunger and piston and it does not need a spring to counterbalance the solenoid and return it to a neutral or default position, but constant electrical power is required to maintain any valve position if such a reverse-polarity solenoid is used. If electrical power is cut to a solenoid-operated valve, then the valve piston position will move and float according to whichever side of it is subject to more pressure; there will no longer be a complete shut-off; and there will be leakage and cross-contamination as between two or more different or distinct liquid fluids available to the valve. If there is a spring acting as a counterbalance to an electrically charged solenoid, when electrical power is cut, then the force of the spring will cause the valve plunger and piston to automatically revert to their neutral or default position.
If the valve plunger is solenoid driven, there may be a spring at the opposite end of the plunger from the solenoid. In case of liquid fluid entering a valve cavity or fluid passageway that is under pressure, this spring can be made stiff and strong enough to be able to exert a counter-balancing pressure that will be strong enough to prevent the force of the liquid fluid from pushing the valve piston into a position that is not desired. If this spring is made to be more stiff, strong, and resistant to movement, then the solenoid has to be able to generate an electrical field that is, in turn, strong enough to be able to offset and overcome the spring tension without assistance from the force of the fluid. The tension of the spring thus sets the range of the head pressure for the liquid fluid or is calibrated to match the prevailing range of head pressures of the liquid fluid, and the electrical magnetic force of the solenoid is calibrated to match and counterbalance the spring tension.
If a valve is motor or screw driven, rather than solenoid driven, then precise control can be established to allow two or more different and distinct liquid fluids available to the valve to communicate in the valve's cavity or fluid passageway, with a set percentage of each liquid fluid communicating according to the degree to which the motor or screw is applied to move the control or selector rod, also known as the plunger, and the valve piston.
If the valve and its components are preferably made of metal, then they have the advantage of being better able to function correctly at higher temperature ranges than components made of plastic or mixed materials, which have a more limited operational range and may not be capable of functioning correctly and may degrade at higher temperatures. Metal components are more robust and durable than non-metal components. Because of the thermal conductivity of metal, a metal valve and components will also respond to heat exchange from an external source more rapidly and thoroughly than a non-metal valve and components. For examples, this external source may be electrical resistance creating heat or it may be liquid coolant routed from a heating source, such as a fuel oil burner or a spark ignition or compression ignition or other form of combustion engine, or a cooling source, such as a radiator or other air- or liquid-cooling exchange device.
If the valve manifold and valve pistons are all preferably made of the same kind of metal, then they will all expand and retract at the same rate when heated and cooled, best preserving the seals between them at all temperatures and preventing complications from different metallic expansion rates, such as seizure of the piston inside the valve cavity or fluid passageway.
A valve that requires a complete seal of one fluid available to the valve while permitting full flow of a different and distinct fluid available to the valve may demand more movement of the piston and a longer piston stroke than a solenoid operating as the driving force can feasibly deliver or allow. For a solenoid to move the valve piston in these circumstances, the solenoid would have to be comparatively bigger in size. Therefore, it would require additional electricity to activate it, which would render the solenoid operation of the valve impractical in an application, such as an engine mounted in a motor vehicle, which engine has only limited electrical amperage available to operate all of the electrical systems of the engine.